The overall objective of this research is to use computation models to analyze cellular and network processes underlying behavior and behavioral plasticity. Models will be based on empirical data from the neural circuitry that mediates feeding behavior of the marine mollusc Aplysia. This behavior is a useful model system for investigating the generation of complex rhythmic movements as well as the neural basis of motivational states and associative learning. Although many elements of the feeding circuitry have been identified, an analysis of the mechanisms underlying its overall function has not yet been undertaken. The present proposal outlines studies that will investigate the extent to which the current understanding of the circuitry is sufficient to account for features of the behavior, examine the contributions of component processes to neuronal and network dynamics, and examine how modulatory inputs and learning- induced changes in cellular properties alter the function of the circuit. In addition, this project will continue the development and distribution of the SNNAP program (Simulator for Neural Networks and Action Potentials), thereby providing a valuable research and educational tool to the scientific and academic community.